Machine for lapping gears



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United States Patent 3,l42,46) MAGHHNE FOR LAPPING GEARS Hans Rebeslri, Remseheid, Germany, assignor to W. Ferd. Klingeinherg Sohne, Rernseheid, Germany Filed Mar. '7, 1963, Ser. No. 263,571 Claims priority, application Germany Mar. 8, 1962 14 Claims. (Ci. 51-26) The present invention relates to a machine for lapping gears. With machines for lapping gears, especially spiral bevel gears, it is necessary to impart upon the wheels certain movements in addition to their meshing rotation in order to extend the lapping eflect to the entire flank surface. In connection with the production of spiral bevel gears, it is known, when milling the teeth into the soft Wheel body, to produce the wheels so that the flanks contacting each other will have a different curvature, said difierence in curvature resulting in crowned flank bearing surfaces. Without the said additional movements, in other words, if the wheels were lapped in a fixed position, this hearing crown would be lapped off more or less and the gears would bear over the entire length of the flanks, which must under all circumstances be avoided in view of possible errors in installation and displacements under load in installed condition, and the danger of breakage and noisy movement inherent thereto.

The crown of the flanks engaging each other which makes possible the displacement of the wheels during the movement without material interference with the intermesh, must therefore under all circumstances be retained during the lapping operation. In addition thereto it must be possible to control the lapping operation by proper selection and coordination of the additional movements with regard to each other in such a way that it will be possible to correct at least to a certain extent distorted contact patterns as they may be the result of a distortion of the wheel body and the teeth during the hardening operation, in other words, it must be possible after such distortion to correct the respective tooth shape to the proper shape and location.

Various types of lapping machines for spiral bevel gears have been produced with various additional movements. The customary additional movements of the wheels relative to each other which, with regard to their dimensions, are of course only small, are primarily the following ones:

(a) A reciprocatory movement in the direction of the axis of the pinion.

(b)A reciprocatory movement in the direction of the axis of the wheel.

(0) A movement perpendicular to the plane of said two axes (movement in the direction of height).

With another heretofore known machine one additional movement is carried out, namely a movement in the direction of the common pitch cone generatrix of the two wheels in the face gear plane. The guiding means for the head stock carrying out this movement are with this machine adjustable with regard to the cone angle. Further known additional movements are small oscillations of the receiving spindle of one wheel about a fixed axis located in the plane of both spindle axes and perpendicular to the spindle axis. The said receiving spindle thus carries out an oscillation about the spindle axis itself so that a pendulum movement of the receiving spindle and the wheel carried thereby will be obtained. The center of rotation of this movement is in this instance located in the center of the front main bearing of the spindle which bearing forms a pendulum bearing.

With another heretofore known construction, the axis of the oscillating movement is perpendicular to the plane 3,142,940 Patented Aug. 4., 1964 of the axes of both wheel receiving spindles and passes through the point on the intermediate tooth width on the common pitch cone generatrix of the wheels to be lapped, i.e. approximately through the center of the bearing crown.

The movements in the direction of the wheel axes, for instance the movement of the pinion spindle in the direction of the large bevel gear axis or vice versa, are structurally likewise often realized as small pendulum movements about a fixed axis parallel to the axis of the moved spindle. To this end the spindle is suspended in a type of rocker arm.

The drive of the individual movements is eifected in most instances by eccentrics, cams or cam discs through the intervention of sliding blocks, levers and the like. Constructions are known in which all additional movements are carried out by one spindle, and constructions are known in which the additional movements are carried out on both spindles. With a heretofore known construction in which the three additional movements are all carried out by the driving spindle, the said movements are initiated by a single cam disc and are adjustable as to their magnitude by roller guiding means with adjustable angle. The character of the movement is in this instance, of course, likewise determined by the cam for all three movements.

It is, therefore, an object of the present invention to provide a machine for lapping of gears in which the three movements can be individually controlled.

It is another object of this invention to provide a machine as set forth in the preceding paragraph in which each of the three movements can individually be determined in conformity with the respective system of the gears to be lapped.

It is still another object of this invention to provide a machine as set forth in the preceding paragraphs, which is characterized by compactness and strength.

These and other objects and advantages of the inven tion will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 is a side View of a lapping machine according to the present invention.

FIG. 2 is a top view of FIG. 1.

FIG. 3 represents a longitudinal section of the wheel head stock.

FIG. 4 is a cross section taken along the line IVIV of FIG. 3.

FIG. 5 represents a partial longitudinal section through the cam shaft with the cam discs, said section being taken along the line V-V of FIG. 4.

FIG. 6 is a cross section through the cam shaft as taken along the line VI-VI of FIG. 5 but on a larger scale than that of FIG. 5.

FIG. 7 illustrates a section through one of the three transmitting levers, said section being taken along the line VIIVII of FIG. 4.

FIG. 8 is a partial longitudinal section taken along the line VIII-VIII of FIG. 4 but turned by FIG. 9 is a partial section taken along theline 1X-]X of FIG. 8.

FIG. 10 is a diagrammatic illustration of the stroke adjustment for the movement in the face gear plane.

FIG. 11 diagrammatically illustrates how the stroke movements influence each other.

FIG. 12 is a control diagram for the clamping and unclamping of a spring ring used in connection with the present invention.

FIG. 13 is a control diagram for a control shaft used in connection with the present invention.

The lapping machine according to the present invention has three additional movements and, more specifically, one movement each in the direction of the two spindle axes while the third additional movement is effected in a plane perpendicular to said two axes. The said three movements are carried out by one and the same spindle, namely by the large bevel gear spindle which is driven by the pinion spindle in view of the intermesh of the gears to be lapped.

The machine is characterized primarily in that the receiving spindle for one wheel of the wheel pair to be lapped is eccentrically journalled in a sleeve which in its turn is eccentrically journalled in a second sleeve rotatably and longitudinally displaceably mounted in the head stock. The machine according to the invention is furthermore characterized in that both sleeves are driven independently of each other by cams through adjustable intermediate members while both sleeves carry out a pendulum movement about their axes and the outer sleeve carries out a reciprocating movement in the direction of its axis.

For the drive of each of the three movements there are provided two cam discs each which are mounted on a common drive shaft. One of said cam discs is effective when the right flank is engaged, whereas the other one is effective when the left flank is engaged.

This construction has over heretofore known designs the advantage of being extremely compact and rigid and makes it possible to control each movement in conformity with the characteristic desired for the respective tooth system of the wheels to be lapped. The movements are conveyed to the sleeves or threaded bushings the cam discs and levers and connecting rods which are adjustable as to their effective length. The said threaded bushing converts the reciprocating movement through a thread into a longitudinal movement of the spindle.

Referring now to the drawings in detail, the machine illustrated therein comprises a bed 1 which, in customary manner, houses the container for the lapping substance and also the pump which conveys the lapping substance through conduit means to the intermeshing portion of gears 4 and 5 which are to be lapped and are supported by the spindles 2 and 3 respectively. Spindle 3 is driven by a motor 7 through the intervention of a V-belt 6, said motor being flanged to an intermediate member 8. The spindles 2 and 3 are respectively journalled in head stocks 9 and 10 which on the upper side of bed 1 are guided on guiding means 11 and 12 extending perpendicular to each other and are adjustable by means of hand Wheels 13 and 14 through the intervention of transport spindles and nuts not shown in the drawings. Manually operable levers 15 and 16 are provided for actuating clamping devices (not shown) for the head stocks on guiding means 11 and 12. Spindle 3 is eccentrically journalled on its head stock in a rotatable drum 17. By turning drum 17 through the intervention of a worm and worm wheel on a square head 18, the spindle axis may for purposes of lapping axis-oifset-transmissions be adjusted above or below the axis of spindle 2.

FIGS. 3 and 4 illustrate the arrangement of the journalling for spindle 2 receiving the larger bevel gear in head stock The outer side walls and lid shown in FIGS. 1 and 2 have been omitted in FIGS. 3 and 4. Spindle 2 is journalled in antifriction bearings 19 and 2-9 in sleeve 21 so as to be slightly eccentric by the distance e Sleeve 21 in its turn is by the same distance 2 eccentrically journalied in antifriction bearings 22 and 23 in a second sleeve 24. The axes of spindle 2, of inner sleeve 21 and outer sleeve 24 which are parallel to each other when in their Zero position, i.e. the starting position of all movements of displacement, occupy the position which in the cross sectional plane (FIG. 4) are indicated by the points of intersection O 0 and 0 The axis of inner sleeve 21 thus extends above the axis of spindle 2 by the distance e and the axis of the outer sleeve 24 extends laterally of the axis of sleeve 21 by the same distance e =e The outer sleeve 24 is rotatable in antifriction bearings 25 and 26 in the head stock housing 9 and is longitudinally displaceable by a small distance. Rotatably mounted on sleeve 24 is a threaded bushing 27 which is axially fixedly located between a thrust bearing 28 and an abutment surface iia of a sleeve 89. This threaded bushing screws in inner thread of a large annular nut 29 which may be axially arrested by a spring ring 30 as will be explained further below. Spindle 2 is driven through the intervention of a pulley 33, which in its turn may be driven by a motor and double V-belt, for creating the lap torque which produces the lap pressure between the flanks. A drive of this type is disclosed for instance in Patent No. 2,904,934.

Screwed to threaded bushing 2'? is a small stand 34 in which is mounted a bolt 35 carrying a roller 36. Said stand 34 furthermore carries a second bolt 37 which is engaged by connecting rod 38. The ends of connecting rod 38 are respectively journalled on bolts 37 and 40 on a ball cup 39 as shown on a larger scale in FIG. 7. This mounting permits a rotation of the connecting rod 38 about the center of the ball cup. Bolt 40 (FIGS. 4 and 7) is adjustable on a lever 42 which is tiltable about a pivot 41. Bolt 46 which has a dove-tailed end guided in a corresponding groove 43 is mounted in an intermediate member 45 provided with teeth 44. After a clamping screw 40:: has been loosened, the intermediate member 45 may be adjusted for purposes of changing the length of lever 42. This adjustment may be effected by means of a pinion 46 journalled in lever 42 and provided with a square head 46a. Lever 42 carries a pivot 47 on which a roller 48 is rotatably journalled. Roller 48 engages a cam disc 5% which is connected to a cam shaft 49. A roller 53 journalled in the fork-shaped end of a plunger 54 presses against the roller 36 in the stand 34. Plunger 54 is reciprocable in a cylinder 55 adapted to be actuated by oil under pressure from an oil accumulator (not shown). In this way, roller 48 will through the intervention of roller 53, connecting rod 38 and lever 42 continuously be held in contact with cam disc 50 so that the position and the movement of the threaded bushing 27 will always be determined by cam. discs 5%.

Similarly, in other words by an arrangement similar to that described, also the inner and outer sleeves 21 and 24 will by cam discs 51a, 51b, 52a. 52b on cam shaft 49 be oscillated about axes 0 and 0 It will thus be evident that there are actually three plungers 54, three connecting rods 38, three levers 42 and three rollers 48.

As will be evident from FIG. 3, connected to the inner sleeve 21 is a stand 56 which similar to the stand 34 carries a bolt 37a engaged by a connecting rod 38a. Similarly, the outer sleeve 24 has connected thereto a stand 57 with a bolt 37b engaged by a connecting rod 38b.

With regard to FIG. 5, it will be noted that mounted on cam shaft 49 and spaced by spacer bushings 81a, 81b, 31c, 81d, Sle, 81 and 81g are six cam discs 50a, 50b, 51a, 51b, 52a, 52b. These cam discs are in a manner shown in FIG. 6 slotted similar to the said intermediate bushings so that they can easily be slipped onto the cam shaft or removed therefrom. A nut 58 clamps the entire packet of cam discs and spacer bushings against a collar 49:: on shaft 49. Each two cam discs are evenly spaced from each other. Cam shaft 49 is rotatable and is journalled in the head stock housing in antifriction bearings 59 and 6% so as to be displaceable by the distance between the cam discs. A plunger 61 which is operable by oil under pressure and which is alternately acted upon during the automatic working operation reciprocates the cam shaft 49 and thereby moves one or the other disc of each pair of cam discs in front of rollers 48 mounted on levers 42. In order to realize such movement without laterally engaging the cam discs or rollers, a continuous straight rail 62 is arranged in the slots of the cam discs. Said rail 62 while likewise rotating with the cam shaft 49 does not take part in the longitudinal displacement of the cam discs. This rail, the outer circumference of which is coaxial with the cam shaft 49, by its radius determines the zero position of all movements. The pressure of rollers 48 is conveyed through an antifriction bearing 63 onto an intermediate member 82 which is screwed to cam shaft 49 by screws 83.

Cam shaft 49 is driven by a small transmission motor 64 (FIG. 4) through the intervention of a V-belt 65, Worm 66 and worm wheel 67. The circuit for motor 64 can be closed only when one of the two limit switches 68 or 69 is closed by contact ring 70 on cam shaft 49, in other words, the motor can start only when the cam shaft 49 occupies one of its end positions but cannot start when said cam shaft occupies an intermediate position. Inasmuch as motor 64 each time after a complete revolution of the cam shaft 49 is turned oif in zero position of said cam shaft, i.e. when rollers 43 rest on rail 62, and inasmuch as the displacement of the cam shaft by piston 61 is always eifected in this position, a lateral engagement of the cam disc with the rollers will be impossible. The turning off of motor 64 after each complete revolution of cam shaft 49 may be effected in any convenient manner, for instance by a cam. This may form a part of the automatic control system of the machine.

For purposes of axially locating the ring nut 29 in the spindle head housing 9 there is provided a two-sectional clamping ring 30 (FIGS. 3, 8 and 9), which is located in a circumferential groove of the nut 29. Said ring 30 is during the operation of the machine spread apart by a wedge member 72 screwed to piston 71 by means of a threaded bolt 71a. This spreading action is brought about by a strong dish spring 73 so that ring 30 is frictionally firmly connected to the inner wall of the housing. The clamping action can be made ineffective by conveying oil under pressure to the other side 7112 of piston 71 against the thrust of spring 73. Ring nut 29 is secured against undesired rotation by the flattened end of a bolt '75 which end extends in a longitudinal groove 74. Bolt 75 has a bore therethrough for discharging leakage oil.

Each axial play in longitudinal direction of the outer sleeve 24 in the threaded bushing 29 and in the annular groove is eliminated by a plurality of oil pressure operable plungers 76 which are distributed over the circumference of sleeve 24 and through the intervention of rollers 77 act against pressure members 78 (FIG. 3) connected to sleeve 24. The axial force exerted by said plungers 76 overcomes a counter force produced by a plurality of springs 79 distributed over the circumference of sleeve 24 and engaging ring nut 29. Said springs 79, however, when the pressure on plungers 76 has been released and pressure acts upon piston 71, will press the then freely movable outer sleeve 24 forwardly and thereby also spindle 2 through the intervention of the inner u sleeve 21. As a result thereof, the larger bevel gear 4 on spindle 2 will be brought into play-free mesh with the teeth of pinion on spindle 3. If then spindles 2 and 3-are rotated slowly, spindle 2 will move in its axial direction against the pressure of springs 79 if a lack of precision prevails, for instance if the outer diameter of the teeth is not round or untrue. This axial displacement, which may be termed two-flank rolling error, may be indicated by a fine indicator or pointer. In this way the improvement in the running properties obtained by the lapping operation as far as it is indicated by the twoflank rolling test can directly be ascertained on the machine. Furthermore, this arrangement makes it possible prior to the start of the lapping operation to adjust the tooth play while taking into consideration the prevailing error in the face runout of the wheels. The operation of the lapping machine as determined by the described devices will be evident from the preceding description.

The shape of the cam discs and the magnitude to be (6,, =pitch cone angle of pinion, FIG. 10). The movement will then be eifected completely parallel to the plane wheel pitch plane. The components of movement in the direction of the respective other movement (FIG. 11) as determined by the oscillation of the wheel axis along an arc about axis 0 and along an are about axis 0 are with an expedient selection of the eccentricities negligibly small with regard to the stroke of the oscillation. According to FIG. 11, the following equation applies:

= tan 5 1 2 Ah=e(1 cos easince is a small angle when is small. Inasmuch as A N l 2e hz A h With a ratio of there results: Ah-0.0125h, which means for h=1 millimeter Ah is only 0.0125 millimeter. This is practically irrelevant.

Referring now to FIG. 12 representing a control diagram of the clamping and unclamping of ring 30, the said diagram shows a contact for opening and closing the circuit of the electromagnetically operable diagrammatically illustrated valve 84 in the pressure conduit for the hydraulic piston 71. When contact 85 is open as illustrated in FIG. 12, the oil may be discharged from piston 71 through the discharge conduit 97. Spring 73 will then through the intervention of wedge member 72 clamp fast ring 30 in the housing.

When contact 85 is closed, valve 84 separates the conduit leading to piston 71 from the discharge conduit 97 while establishing communication between the conduit leading to piston 71 with the pressure conduit 96. As a result thereof, the piston 71 compresses the spring and releases the wedge member 72 whereby the ring 30 is unclamped.

Contact 85 may be actuated either manually, for instance by means of a push button or a limit switch (not illustrated) adapted to be actuated by the head stock 10 carrying the pinion 3. Such actuation would take place when the head stock during the automatic operation of the machine moves into working position. Push button and limit switch act upon a relay (not illustrated) which in turn controls the closing and opening of contact 85.

Referring now to FIG. 13 illustrating a control diagram for the drive of control shaft 49, it will be noted that this simplified diagram comprises a control cam 86 which, merely for purposes of simplicity, has been shown as being mounted on a collar of the driving worm Wheel 67. However, it will be appreciated that the said control cam could as well, as illustrated in FIG. 5, be mounted on another part rotating with the control shaft. Control cam 86 will, when control shaft 4% is in its zero position, i.e. in the position in which the rollers 43 rest on rail 62, actuate a limit switch 57. The arrangement shown in FIG. 13 furthermore comprises two electromagnetically operable reversing valves 88 and 89 which control the supply of oil under pressure from conduit 94 to the cylinder chambers on the leftand right-hand side of piston 61 and also control the discharge of the oil from said cylinder chambers to the discharge conduit 95. The arrangement furthermore comprises a counter 93 which, with each rotation of the control shaft 49 receives an impulse by cam 86 and limit switch 87 and which actuates the switch 90 in conformity with the completion of a predetermined number of revolutions for which the counter has been set. Switch ti is located in the circuit of the magnets for the reversing valves 88 and 3% and depending on its position brings about that oil under pressure from conduit 94 will be able to pass to the respective cylinder chamber on the right hand or left hand of piston 61 so that the respective cylinder chamber not under pressure will communicate with the discharge conduit 95. The control shaft with cam discs 50 to 52 will then be moved from its respective working position into another working position.

Limit switch 87 has a double function. it assures that the displacement of the control shaft can be effected only when it is actuated by cam 86, i.e. when the rollers 48 rest on rail 62. On the other hand, said limit switch 87 will, with each revolution of the control shaft,

impart an impulse onto the counter 93 which latter will then initiate the displacement of the control shaft after a certain number of revolutions of the control shaft in conformity with the setting of the counter.

The automatic turning on and turning off of motor 64 is likewise controlled by counter 93 which latter in conformity with the set number of revolutions for the control shaft closes switch 91 in the energizing circuit of control relay 92 of the motor. It should be noted, however, that relay 92 can be energized only when in addition to switch 91 also one of the two contacts 68 and 69 has been closed by ring 79 on control shaft 49, i.e. when the control shaft is in its right-hand or left-hand end position. in this way, motor 64 is prevented from operating while the control shaft is being displaced.

It is, of course, to be understood that the present invention is, by no means, limited to the particular constructions shown in the drawings but also comprises any modifications within the scope of the appended claims.

What I claim is:

1. In a machine for lapping gears, especially spiral bevel gears: a housing, bearing means mounted in said housing, first sleeve means rotatably journalled in said bearing means, second sleeve means eccentrically and rotatably journalled in said first sleeve means, means for preventing axial displacement of one of said sleeve means while the other one of said sleeve means is axially displaceable, spindle means for receiving one of said gears to be lapped, said spindle means being eccentrically and rotatably journalled in said second sleeve means, means for preventing axial movement of said spindle means relative to said first and second sleeve means, first and second actuating means respectively operatively connected to said first and second sleeve means for individually oscillating the same about the respective longitudinal axis thereof, and third actuating means operatively connected to the other one of said sleeve means for imparting thereupon a reciprocatory movement in axial direction thereof.

2. A machine according to claim 1, in which said second sleeve means is prevented from axial displacement and in which said third actuating means is operatively connected to said first sleeve means.

3. A machine according to claim 1, in which each of said first, second and third actuating means comprises a train of elements at least one of which is adjustable.

On one hand 4. In a machine for lapping gears, especially spiral bevel gears: a housing, bearing means mounted in said housing, first sleeve means rotatably journalled in said bearing means, second sleeve means eccentrically and rotatably journalled in said first sleeve means, means for preventing axial displacement of one of said sleeve means while the other one of said sleeve means is axially displaceable, spindle means for receiving one of said gears to be lapped, said spindle means being eccentrically and rotatably journal-led in said second sleeve means, means for preventing axial movement of said spindle means relative to said first and second sleeve means, first and second actuating means respectively operatively connected to said first and second sleeve means for individually oscillating the same about the respective longitudinal axis thereof, third actuating means operatively connected to the other one of said sleeve means for imparting thereupon a reciprocatory movement in axial direction thereof, each of said first and second and third actuating means including a pair of cams, and a cam shaft common to all of said cams, one cam of each pair of cams being operable in connection with the lapping of one flank of a tooth to be lapped and the other cam of each pair of cams being operable in connection with the lapping of the other flank of the same tooth to be lapped.

5. A machine according to claim 4, which includes fluid operable cylinder piston means operatively connected to said cam shaft for moving the same in axial direction for alternately making one cam of each pair of cams effective.

6. A machine according to claim 1, in which said first and second and third actuating means each comprise a train of elements including a cam and a connecting rod operatively connected to the respective sleeve means and also including adjustable lever means interposed between the respective cam and connecting rod.

7. A machine according to claim 6, which includes roller means carried by said lever means for engagement with the respective cam pertaining thereto, and fluid operable piston means continuously holding said roller means in engagement with the respective cam pertaining thereto.

8. In a machine for lapping gears, especially spiral bevel gears: a head stock housing, bearing means mounted in said housing, first sleeve means rotatably journalled in said bearing means, second sleeve means eccentrically and rotatably journalled in said first sleeve means, means for preventing axial displacement of said second sleeve means, said first sleeve means being axially displaceable, spindle means for receiving one of said gears to be lapped, said spindle means being eccentfrically and rotatably journalled in said second sleeve means, means for preventing axial movement of said spindle means relative to said first and second sleeve means, first and second actuating means respectively operatively connected to said first and second sleeve means for individually oscillating the same about the respective longitudinal axis thereof, third sleeve means journalled on said first sleeve means and having its outer periphery provided with a thread, nut means threadedly engaging the thread of said third sleeve means and interposed between the latter and said housing, means for alternately effecting a connection and disconnection of said out means with said housing, third actuating means operatively connected to said third sleeve means and operable to impart thereupon an oscillating movement when said nut means is connected to said housing to thereby impart upon said first sleeve means a reciprocatory movement in axial direction thereof.

9. A machine according to claim 8, in which said not means is axially displaceable and is connectable to said housing in its respective axially displaced position.

10. A machine according to claim 8, in which said nut means is provided with a circumferential groove, and which includes a resilient split ring confining between its ends a wedge-shapecl gap and being located in said circumferential groove, and spreading means extending into said gap and operable alternately to spread said split ring and to permit the latter to contract.

11. A machine according to claim 10, which includes dish spring means for continuously urging said spreading means into said gap, and which also includes fluid operable means operable to contract said spring means to thereby permit said split ring to contract.

12. A machine according to claim 8, which includes a plurality of fluid operable cylinder piston means distributed over the circumference of said first sleeve means and operatively connected to said first sleeve means for imparting thereon an axial movement in one direction to eliminate the backlash between said nut means and said third sleeve means threadedly engaged thereby.

13. A machine according to claim 12, which includes spring means continuously urging said nut means in a direction opposite to said one direction.

14. A machine according to claim 1, which includes an additional gear receiving spindle, motor means for driving said two spindles, said motor means including an infinitely variable motor drivingly connected to one of said two spindles for producing a variable lap torque in both directions.

References Cited in the file of this patent UNITED STATES PATENTS 2,111,170 Condon Mar. 15, 1938 

1. IN A MACHINE FOR LAPPING GEARS, ESPECIALLY SPIRAL BEVEL GEARS: A HOUSING, BEARING MEANS MOUNTED IN SAID HOUSING, FIRST SLEEVE MEANS ROTATABLY JOURNALLED IN SAID BEARING MEANS, SECOND SLEEVE MEANS ECCENTRICALLY AND ROTATABLY JOURNALLED IN SAID FIRST SLEEVE MEANS, MEANS FOR PREVENTING AXIAL DISPLACEMENT OF ONE OF SAID SLEEVE MEANS WHILE THE OTHER ONE OF SAID SLEEVE MEANS IS AXIALLY DISPLACEABLE, SPINDLE MEANS FOR RECEIVING ONE OF SAID GEARS TO BE LAPPED, SAID SPINDLE MEANS BEING ECCENTRICALLY AND ROTATABLY JOURNALLED IN SAID SECOND SLEEVE MEANS, MEANS FOR PREVENTING AXIAL MOVEMENT OF SAID SPINDLE MEANS RELATIVE TO SAID FIRST AND SECOND SLEEVE MEANS, FIRST AND SECOND ACTUATING MEANS RESPECTIVELY OPERATIVELY CONNECTED TO SAID FIRST AND SECOND SLEEVE MEANS FOR INDIVIDUALLY OSCILLATING THE SAME ABOUT THE RESPECTIVE LONGITUDINAL AXIS THEREOF, AND THIRD ACTUATING MEANS OPERATIVELY CONNECTED TO THE OTHER ONE OF SAID SLEEVE MEANS FOR IMPARTING THEREUPON A RECIPROCATORY MOVEMENT IN AXIAL DIRECTION THEREOF. 